Commercial Bodywork
A series of articles
by the Chief Bodywork Designer for Morris Commercial Cars Ltd, T.
Evans, appeared in Morris Commercial publications in the
mid-1930's. As some of the information contained therein is of
particular interest to members restoring commercial vehicles,
extracts are reproduced here.
In the selection of suitable materials for body construction
the weight factor plays a highly important part, for whilst
certain extremely light alloys cannot always be employed by
reason of their comparatively high cost, much can be and is being
achieved by a careful study of the more orthodox materials.
Metal construction has - during recent years - made a marked
advance, but for commercial bodywork, timber is still the main
raw material, and for all classes of framework colonial, and
American ash is used extensively, being strong, durable and
considerably lighter than either English ash or oak. Now whilst
these timbers have a higher strength factor of value in such
applications as heavy vehicle bottom frames, the colonial ash has
certainly proved its efficiency for a very high percentage of
general framing members. Canadian yellow birch is also used to a
large extent in this country and compares very favourably with
ash but is slightly heavier. Red beech is also sometimes used for
the lesser items of framework and compared with ash is about
equal in weight, although certainly not as durable.
Most Suitable Timber
All factors considered, therefore, a good quality colonial ash is
the most suitable timber in this connection particularly where
the total weight has to be maintained at a minimum. Many of the
lesser known timbers of both empire and foreign origin have been
tried, and whilst certain of them compare very favourably with
ash, only one in the writer's experience, namely 'serayah,' shows
any appreciable saving in weight and is, therefore, a very useful
material for, say, bulk capacity or pan-technicon framework,
where this question is of vital importance (origin - Borneo and
the Malay peninsula).
Softwoods are used principally for floors, roofing and truck
sides, deal, spruce and British Columbian pine being the three
most useful timbers in these applications. Silver spruce is the
lightest and may be used successfully for truck sides, roofing,
bearded partitions and interior fixtures generally. It is not,
however, quite as strong as red deal or B.C. pine, these
materials being, therefore, more suitable for truck or van
floors.

PICTURE: Modern treatment of the fronts of bulk
capacity bodies greatly enhances the general appearance.
The
exterior panelling of van bodies also contributes
considerably to the total weight, particularly on large
three- or four-ton bulk capacity vans where some 250 so.
ft. are required. At the present day, however, we have a
number of excellent materials from which to choose,
thanks to the progress made by various firms specialising
in their manufacture, and the following list shows at a
glance the weight saving that can be affected in this
section of construction even though a little extra cost
is entailed:-
| lb. per sq. ft | ||
| Silver finished steel sheets | 20 s.w.g | 1.47 |
| Aluminium sheets | 16 s.w.g | 0.9 |
| Aluminium sheets | 18 s.w.g | 0.875 |
| Single faced steel amour ply | 1/8 in. | 1.16 |
| Single faced steel amour ply | 3/16 in. | 1.39 |
| Single faced aluminium amour ply | 1/8 in. | 0.7 |
| Sundeala board | 3/8 in. | 1.25 |
| Masonite board | 3/16 in. | 1.062 |
Turning to the
various metals employed, steel is still used in most cases for
all kinds of fittings and reinforcements for, as previously
mentioned, certain very excellent light alloys have a cost
disadvantage sufficient to retard their adoption generally. Their
value in certain specific applications is, however, easily
appreciated when one considers that a metal such as duralumin is
equal in strength to steel and only one-third the weight.
Aluminium of varying grades is also used extensively for
mouldings and various fittings - again in the interests of weight
reduction.
Bottom Frames
The bottom
frame of most bodies is usually the heaviest section,
particularly on truck type bodies having a flat platform, for
here the depth of the runners and cross bars is governed to a
certain extent by the requisite clearance over the rear road
wheels, and not entirely by their sectional strength
requirements.
Much can be achieved, however, but careful distribution of the
cross members in proportion to the body length, and a definite
saving is also registered by designing the intermediate members
as parallel edged members fitted with making up pieces at each
side where they rest upon the longitudinals, instead of cutting
them out of a deep solid bar.

PICTURE: Demonstrating the relationship between
immediate pillars, crossbars, and roof sticks in the construction
of van framing.
The
longitudinal runners may be lightened by cutting down
their depth a little between cross members as they are
supported through practically the whole of their length
by the chassis frame, but any overhanging portion at the
rear may, of course, be maintained at the full section.
The bottom framework of van bodies is a much simpler
problem from a weight aspect as wheel arches are usually
permitted in their design, and the longitudinal members
may, therefore, be dispensed with, support for the rear
of the body being obtained by the extension of the
chassis frame side members.
As regards what may be termed the upper structure of van
type bodies, which include the side, front and roof
framing, efficient distribution of framing members is
highly important to attain strength coupled with
lightness. Thus better results are frequently obtained by
keeping the intermediate pillars, rails and roof sticks
light in section but spaced at reasonable intervals than
by fitting an inadequate number of heavier section
members. This latter principle results in no saving in
weight as compared with the former and provides less
support than necessary for the side panels and roof
covering.
Correct Jointing Methods
Light framing also compels the adoption of correct jointing
methods for, as previously pointed out, the ultimate resistance
of most members to any individual stress is governed by their
sectional strength at the points where they are jointed to other
members. For this reason it is customary to proportion the
vertical pillars of van bodies considerably more in width than
thickness. The laps may then be safely cut on the outer face to
receive the various longitudinal rails that must pass across
them.
This
also permits the rails to be maintained at a minimum
section, for no more than is necessary to provide a
location need be cut out at their joints, as the major
portion of the lap is taken out of the pillar.
In the construction of all types of doors, weight should
be cut down wherever possible for, in addition to the
general interest, a heavy door imposes such work as will
necessitate stronger, and therefore heavier, hinges,
locks and dovetails. The various framework members
should, therefore, be lightened out where possible,
implying that in many instances a certain section of
bottom rail is necessary to ensure a strong lapped joint
on to the pillars but nevertheless allowing a reduction
to be made between the joints without in any way
impairing the strength of the completed assembly.
Large van rear doors call for a strong framework securely
jointed to prevent a natural tendency to whip or twist
but rather than increase the section of the members
excessively, it is a better practice to line the door on
the inside with a light plywood securely fastened to the
framework. The additional stiffness obtained by this
method results not only in a light structure but also in
an exceedingly strong one.

PICTURE: Detail parts of a forward-control cab
side assembly showing the amount of accurate machining required.
Truck Bodies
Truck sides
and tailboards should be strongly hinged to the lower framework,
and also be quickly and easily detachable, as certain loads
necessitate their complete removal. In this connection, whilst it
may be good design to fit rigid and permanent centre and rear
corner posts on long heavy vehicle bodies, they should not be
included on the lighter or even medium capacity trucks, in view
of the obstruction they present when the vehicle is being
operated in this manner.
The sides on most modern truck bodies are of sufficient depth to
allow an interior height of approximately 18 in. and they are
usually reinforced to take the stress of bulging loads in
proportion to their length. Strict attention is also paid to the
fitting of protection plates to the edges, also to the top edge
of the chock rails, and at intervals across the platform, as
these add considerably to the life of the parts concerned.
Touching on the general design and construction of tipping
bodies, we again find a very marked advance, particularly in
respect of the actual tipping gear. On the hand-operated type we
now have the screw universally mounted, allowing self alignment
should the body be tipped with the vehicle standing on uneven
ground. In addition, the latest designs of power-operated gears
have so proved their efficiency as definitely to justify the
extra capital outlay involved, particularly on vehicles of over
two tons capacity.
Van Bodies
Under
the heading of van bodies we have an even greater variety
of types than in the case of the trucks, but, in a like
manner, we find on examination distinct essentials that
form the basis on which most van type bodies are
designed. First again in order of importance is the
question of load space, and in this instance we are
concerned more with cubic capacity than with actual
platform area. Further, these three governing interior
dimensions - length, width, and height - have a very
important bearing on the general balance and finished
appearance of the completed body. We are also faced with
the fact that the height of the load is in many cases
equal or greater than the width, thus affecting the
general stability of the vehicle.

PICTURE: Rear overhang of the bottom framework
of a van body showing the straight-through longitudinal members.
Accessibility
Another
item calling for keen attention is the general accessibility
affecting loading and unloading. The almost universal method
adopted today is through the rear of the van, side arrangements
being principally used as extra means of access on large or
special type bodies. The rear doorway should conform as nearly as
possible to the interior dimensions of the body. This is most
essential for example on bakers' and confectioners' vehicles.
Full height double doors are now fitted to a high percentage of
vans of all types to ensure complete protection of the goods
carried. The spring roller shutter has also proved its popularity
in this connection, being exceptionally quick and easy to operate
- the only drawback to this method being the additional height
required to house the shutter above the rear aperture when open,
but where, as in most cases, bodies are not loaded to their
extreme interior height, this factor remains of little
consequence.
General Appearance
Having
covered, to some extent, the practical requirements of commercial
bodywork, we can now consider general lines and finished
appearance which, as previously noted, have improved beyond all
measure during recent times. This feature is perhaps most
apparent to us on the smaller vehicles, and can doubtless be
attributed to their general proportions being more adaptable in
this respect.
With the larger bodies, however, one also notices a very marked
improvement. Let us take, for example, the present day treatment
of the front portion of bulk capacity and pantechnicon type
bodies. A generous slope is given to the windscreen and front
panel of the compartment above the driver's cab - this line,
terminating in a well proportioned radius over the roof corner,
and coupled with similar radiused panels on each of the side
corners, results in a very pleasing and smart appearance.
Incidentally, this manner of treatment to the fronts of large
bodies reduces the air resistance set up by large frontal
surfaces, with obviously beneficial operating results.
The separate driver's cab used in conjunction with all manner of
truck bodies provides another striking example of the better
finish and general appearance that is now achieved. In fact, this
particular item is subjected to practically the same treatment
today as the private car, as we have a true streamline to the
scuttle and cab sides, a sloping windscreen and domed roof and
rear corners.
Assembling the Framework
Special
jigs are used to ensure accuracy and correct fitting together of
the various joints.
In order to appreciate fully the efficiency attained by this
method of constructing body framework, let us visualise, for
example, the type of jig used for a light van side assembly. This
section is usually built with a front vertical pillar, three
intermediate and one rear pillar, four longitudinal rails
consisting of one lower skirt rail, two waist or moulding rails,
and one top or- to use the correct term - cant rail. There is
also the longitudinal bottom side-which is the member that
connects up with the floor of the body, and also the bent wood
rail known as the wheel-arch bend.
The jig used to ensure correct jointing together of these parts
into one complete van side framework is built up on a
trestle-like structure at a height convenient for the workmen,
and is fitted with location blocks which maintain the positions
of the parts mentioned in correct relation to each other.
Various forms of clamping devices are fitted where necessary to
grip the joints firmly together before they are secured by the
screws or bolts, whichever may be the case. These methods of
assembly, as one can appreciate, ensure that all body units will
be perfectly true and accurate, factors having an important
bearing on the final assembly, as incorrect lining up of the
framework in the initial stages would result in harmful pent-up
stresses at various points of the body when completely assembled.
Service Considerations
The principle of standardising various constructional parts and
fittings on different models also facilitates maintenance,
particularly for large fleet owners whose vehicles are equipped
with various types of bodies. In this connection, for example,
the driver's compartment door is today identical on all
Morris-Commercial normal control vans and trucks from 15 cwt. up
to 3% tons capacity. (Morris Commercial C-type).
This arrangement is of great assistance in servicing such parts
as drop window mechanisms, locks and buffers. The same principle
is carried out, if not quite to the same extent, on such items as
windscreens, cushions and a considerable number of smaller body
components.
Constructing Body Framework
The sides
and tailboards of most truck bodies of a capacity up to and
including 3 tons, are constructed of a number of tongued and
grooved boards held together by vertical hardwood battens on the
inner face, and by the hinge irons on the outer face. In deciding
on the number of boards to use for making up a complete side or
tailboard, the possibility of shrinkage should be considered as
joints that have opened are weak and impair the general
appearance.
Whilst it is not possible completely to control shrinkage, a
little forethought will minimise the effects produced. For
example, a 15 in. side made up of four 3314 in, boards will be
more satisfactory in this respect than three 5 in. boards, the
reason being perfectly clear on considering for a moment why
timber alters under varying conditions.
Effects of Moisture
First, the
moisture content of most exposed timber structures is governed
largely by the existing atmospheric conditions. In warm, dry
weather, therefore, moisture is dried out and shrinkage of the
boards takes place. As shrinkage is a function of the width of a
board it will be appreciated that a reduction in the width of a
board correspondingly reduces its absolute shrinkage and,
therefore, an assembly constructed of narrow boards will show at
each joint a smaller shrinkage gap than a similar assembly
consisting of wider boards. In either case the total shrinkage
would be the same, but narrower boards, necessitating a greater
number of gaps, show a proportionately smaller gap at each joint.
The hinges fitted to both sides and tailboards are perhaps the
most important items of truck ironwork as, apart from hinging the
sections referred to, they also act as a reinforcement and, in
view of this, the section of the material used should receive due
consideration. Most of the stress on these hinges is applied at
right angles to their face and if, as is commonly found, flat
section steel is selected for the manufacture of these parts the
thickness must be-from the writer's experience it should not be
less than 3/8 in. - as to afford adequate strength.
On sides over 9 ft. in length we find some extra reinforcement
necessary if effective resistance is to be offered to loads of a
bulging nature. This can be obtained by fitting a mild steel
angle - or preferably channel section - along the top edge, or by
securing a timber rail in the same position having a wide convex
section steel top capping.
Van Bodywork
The
majority of van bodies today have arches constructed over the
rear road wheels, thus permitting the lowest load line possible
to be obtained consistent with suitable bottom frame
construction. A series of cross members spaced at intervals from
front to rear contribute the major portion of the support, and
they must therefore, have a correct sectional strength, in
accordance with the load capacity of the particular body in
question, plus a safety factor ensuring efficient resistance to
the additional forces. On the other hand, however, their depth
should certainly not be more than conditions demand or the load
line will, of course, suffer accordingly, apart from the weight
factor which must at all times be taken into full account and
kept as low as possible.
This
question of providing sufficient strength at a minimum of
sectional depth calls for extreme care in the methods
adopted for jointing the various framework parts;
otherwise a large proportion of the intended strength is
wasted. In this connection no better example can be taken
than an instance of where the body overhangs the chassis
frame to a considerable extent at the rear. Here, it will
be appreciated, substantial longitudinal members must be
included in the bottom framework, arranged to register
and to take their support from the chassis frame side
members, but extended beyond them to carry the rear of
the body.
Under such conditions we find these members are stressed
to an even greater extent than those arranged
transversely - particularly where they leave the end of
the chassis frame. While on many chassis, frame design
permits metal extensions to be secured in such a manner
as to provide adequate support , others are not so
adaptable in this respect.

PICTURE: A van side assembly jig showing a
completed side framework lifted out.
With a construction of this type cross members cannot be placed
on top of the longitudinals as this course would make it
impossible to obtain a low floor level. They must therefore be
jointed across or into each other in such a manner that little or
no increase in the overall height of the frame results.
In this application the practice known as 'half lapping' is
successfully used, providing the strength of each member at the
points where the laps are cut is adequate. This cannot always be
obtained; for instance, should a cross member be required to
register with the end of the chassis frame, a joint of this
description would weaken the longitudinal member by half at the
exact point at which the maximum stress occurs.
Rear Frame Treatment
Excellent
results can be and are achieved in such instances by the
application of suitable metal reinforcement ensuring the required
distribution of the load imposed.
Even better results can be obtained by individual attention, and
the sketch here shows the Morris- Commercial method. Here, it
will be noticed, the body cross member falls over the rear cross
member of the chassis frame, and it is, therefore, possible to
split this member into three sections by taking advantage of the
support by such a useful relationship of members. This permits
the longitudinals to pass through the cross member and retain
their full sectional strength throughout with only a light metal
reinforcement as a safety factor.
The two outer sections of the cross member are, it will be
noticed, bolted to the overhanging part of the chassis member,
and as the centre is mainly giving support to the floorboards
passing over it, this is secured by mild steel plates strapped
across the joints.
Reinforcements
The reinforcement of timber members with mild steel plates is
usually employed in cases where additional strength is necessary
without increased dimensions. The longitudinal members are a
striking example of this, and from the writer's experience, a
mild steel angle section correctly applied will give a far higher
strength factor than the usual flat section one often sees
secured to one face of the member. This is easily appreciated
for, in the case of the angle section method. any over-stress
taken on the member is immediately transferred directly to the
reinforcement as it is actually seated on one side of the angle,
whereas with the flat section bolted on the one face only, at
right angles to the direction of stress, reinforcement is
obtained only from the bolts or screws securing the plate to the
actual member and, therefore, the sectional strength of the plate
used is not fully employed.
Side and Roof Framework
With the
general delivery type of van body the side framework is mainly
constructed of vertical pillars and longitudinal rails, the
number of intermediate pillars and rails being largely governed
by the length and height of the complete framework and also by
the type of panelling used. From the strength aspect, however,
which is the prominent feature of these considerations, the
vertical pillars should, wherever possible, be jointed to the
bottom frame side members at points adjoining the cross members.
They can then be secured with bolts and reinforced with light
steel plates - one leg being bolted to the pillar and the other
to the cross member. This same procedure should also be repeated
when positioning the transverse members, or roof sticks, of the
roof-framing, thereby completing a series of cross sectional
frames throughout the body.
It is easy to see the advantages of this system of setting out
van body framework. Apart from providing maximum resistance to
the various stresses, the system ensures a correct distribution
of the work in the respect that each member is receiving support
from the adjoining members.
Tilt Vans
The method of construction usually adopted on the tilt van type
is also particularly successful in this direction, as here one
complete timber rail is bent to form pillars and roof stick.
Returning to considerations of side framework, we generally find
the vertical pillars are greater in their sectional depth than
the longitudinal rails. This is essential to ensure adequate
strength remaining after the lap joints have been cut for the
rails. Providing both parts are suitably proportioned for their
particular purpose and present a flush finish on the outer face
to receive the panelling, any further levelling up results in
unnecessary weight.
Rear Construction
The method
of constructing the rear of a van body is governed - perhaps more
than any other section - by the type of work for which it is
required. On most delivery vans, rounded rear corner panels may
be incorporate without having any ill effect on the loading
facilities, whilst they add considerably to the finished
appearance. The framing necessary in the construction is entirely
suited to the work imposed, and the actual metal panel provides
additional stiffness. Where the type of load demands a rear
aperture equal to the interior width of the body - as is required
by the bakery and confectionery trade - a corner pillar is more
suitable. When service conditions call for rear doors hung on
outrigger hinges, enabling them when open to lie flush against
the body sides, the rounded metal corner is not so suitable for
the mounting of this particular design of hinge.
Many vans, such as the luton and laundry types, which usually
have an interior height of 6 ft. or more, are only fitted with a
drop tailboard and curtains. Here wider section corner pillars
may be fitted, resulting in the exceedingly strong construction
that is so necessary. With all forms of rear framework, however,
it is of common importance that strong, reinforced joints are
obtainable at both the lower and upper corners, for here the
greatest stresses occur in this particular section of
construction.
End Tipping Truck Bodies
The weight
of the load to be carried, its nature, and the manner in which it
must be handled, are the chief factors to be borne in mind in the
design and construction of commercial vehicle bodies generally.
In the case of tipping bodies the last mentioned factor affects
the whole of the construction and the means of attachment of body
to chassis as tipping lorries are designed for the express
purpose of handling materials that cannot be economically
unloaded in the orthodox manner.
In the preliminary layout of any type of tipping body, strict
attention must be given to the question of suitable capacity and
general proportions to ensure an equal load distribution on the
chassis, both when travelling and also when the body is being
lifted for purpose of discharging the load.
Dimensions
Short
wheelbase chassis are mainly used as a basis, permitting an
interior body length between 8 ft. or 9 ft., and varying from 5
ft. 6 in. to 6 ft. 6 in. in width. These dimensions can be taken
as covering vehicles from, say, 30 cwt. up to 4 tons carrying
capacity, the height of the sides being usually greater in the
latter case.
Assuming that suitable interior dimensions have been decided upon
in relation to the chassis and load capacity, the next important
step, to ensure correct proportions, is the fixing of the
location for the rear pivot or hinge centre, which should in all
cases be positioned as close to the rear axle as possible. If
this is aimed at it will be found that the nearest point is
slightly forward of or directly over the back spring rear
bracket.
By pivoting the body about this point load distribution will be
correct not only when the vehicle is travelling but also when the
load is being tipped,as it will be easily appreciated that the
forward placing of the pivot considerably reduces the load on the
lifting gear. Further, and of equal importance, the stress
imposed upon the chassis frame when the body is being tipped is
taken at a strongly supported section, and not on the extreme
ends of the frame side members.
From the writer's experience the correct location of the pivot
usually gives a proportion of two-thirds of the body length
forward of the pivotal point and one-third rear overhang.
Bottom Frame Construction
Strong, soundly constructed bottom framework is essential to the
success of all classes of bodywork but with tipping bodies it is
of exceptional importance as during tipping operations little or
no support is obtained from the chassis frame. The longitudinal
bearers or runners must, therefore, be of sufficient sectional
strength to support the load distributed over their length,
better distribution being achieved by spacing the intermediate
cross members more closely than on the ordinary truck body.
While
considering the necessity of bottom framework strength on
this type of body it is opportune to draw attention to
correct methods of securing the tipping gear and rear
hinges to the body. The rear hinges on most bodies today
consist of two brackets at each side, one being seated
upon and bolted to the top chassis frame side member
flange, and the other secured to the side face of the
body runner, a mild steel bar of not less than 1½ in.
diameter passing through both sets of brackets. In some
cases body brackets take their load only through their
securing bolts. This, it will be appreciated, is not
sound practice and conditions are greatly improved if
small lugs be included in the bracket design providing a
definite seating for the bottom face of the runners and
relieving the securing bolts of direct shearing stresses.

PICTURE: Showing how weight may be saved in
truck bottom framing.
Lifting Bracket Support
With either
the hydraulic ram or hand screw type of tipping gear situated
between the rear of the cab and the front of the body the method
of securing the actual lifting bracket is governed by the same
important strength factors. It is not sufficient for this bracket
to be merely bolted to the front cross member or boards - as is
sometimes seen - but it should be designed with a flange at least
or fitted with additional steel plates that will pass under the
bottom face of the front bar. If this is done the securing bolts
are again relieved of considerable shear stress. Further, no
undue stress is transferred to the front boards of the truck.
On bodies designed for 3-ton loads or more, this distribution of
work should be carried still further, as in the case of the
Morris-Commercial 4-ton tipping model. Here the ram body bracket,
by reason of a specially designed reinforcement, virtually exerts
ifs lift under the front ends of the longitudinal members. This
is achieved by fitting a mild steel angle section support to the
bottom edge of the front cross member, which is set down at each
end, and under the bottom face of the runners, the bolts securing
these members to the front crossbar passing through the
horizontal flange of the angle. The ram bracket, being designed
with a flange at right angles to its vertical face, is,
therefore, when secured in position applying the lift to the
angle support which, as described, distributes it to points each
side under the ends of the longitudinal runners.
The principle underlying this method of lifting heavily bodies is
quickly appreciated if one considers the following factors. The
body and load rest on the longitudinal runners which, in turn,
are supported by the pivot brackets at the rear. Should it be
desired to lift the forward end of the body it is obvious that
the best conditions will result if the supporting runners receive
the force in as direct a manner as possible and not through the
media of various bolts.
Continuing with the general construction of the body, the floor
should in all cases be lined with sheet steel of not less than 18
S.W.G. The requirements of the front head board and hinged side
boards being the same as with most other types of truck bodies,
their construction follows identical lines. The tailboard
requirements, however, are distinctly individual.
Tailboard Features
In the
first instance a tipping body tailboard must hinge from the top.
It should be easily detachable to avoid damage and the securing
arrangement of a type the operation of which is unaffected by
load pressure on the actual board. To facilitate fitting lift-off
hinges it is sound practice to incorporate detachable rear corner
posts; a mild steel round section bar upon which the tailboard is
hung can then be fitted between the posts. An even better method
where corner posts are incorporated is to employ what may be
described as a short section of bar only, secured to each post,
the lift-off hinges on the tailboard being in this case specially
strengthened. The advantage gained by this arrangement is the
unobstructed aperture presented when tipping, an important
advantage as compared with other types. On the standard type of
truck body it is customary for the tailboard to lie between the
ends of the sides when closed, but with tipping bodies, carrying
as they do such loads as sand and fine gravel, it is a decided
improvement to hinge the board so that when it is in the closed
position it completely seals' the rear end of the body, leaving
no clearances and bearing tightly against the end of the sides
and along the rear face of the back bar, a generous overlap being
allowed at this point.

PICTURE: Illustrating the design of the special
Morris-Commercial tailboard locking device in which the hand
lever is unaffected by load stresses.
Various
types of devices are today employed for securing tipper
tailboards but, in the writer's experience, they are 98
per cent. alike in the respect that security is obtained
only after the tailboard has been manually held in the
closed position and some type of cotter or pin inserted
in a slot or eye. With this arrangement difficulties
frequently arise in connection with their removal at the
end of a journey, because of the load having settled down
en route and set up a considerable pressure on the
tailboard.
It is of interest to refer to the type of security device
introduced by Morris Commercial Cars Ltd. on their 4-ton
end tipping model (C-type). Here the full requirements
described are catered for in the respect that a specially
strong toggle action clip is fitted each side. It is
possible to engage the link portion of this device with
the end of a stout metal channel secured to the
tailboard. The handle of the clip may than be pulled
round through approximately 120 degrees, thereby closing
the tailboard hard up against the end of the body. A
safety pin is inserted, purely as a precautionary
measure, to prevent the handle from springing out. The
pin can be placed into position or removed without effort
under all conditions as it is in no way affected by load
pressure.
It should also be noted that the complete security device
is attached to the detachable corner pillars and,
therefore, comes away with them should the vehicle be used as a flat platform. In the event of the tailboard not being
carried on such occasions as when the vehicle may be dealing with
overhanging loads the security device can be completely folded
back snug against the side chock rail and secured with the safety
pin.
The Tipping Gear
Without
describing in detail modern end tipping gears it is extremely
interesting to consider the vast improvements that are now
incorporated by most manufacturers. Hand operated gears are
fitted for instance with universally mounted self-aligning screws
which prevent binding when the vehicle is tipped on uneven
ground. Further, the screws are of the telescopic type which has
the advantage of bringing them well below the height of the
driver's cab.
Power hydraulic gears also represent a distinct advance,
particularly for vehicles of over 2 or 3 tons capacity. Operation
of this type of gear is extremely simple, the controls being so
arranged in the cab that they can be reached with ease from the
driving seat, the oil reservoir being usually located under the
driving seat. An individual feature included in the specification
of the gear fitted to all Morris-Commercial 4-toners is a special
safety catch - entirely automatic - which prevents any
possibility of the body tending to self tip when unladen or in
instances when load is being carried at the extreme rear end of
the truck.
Bibliography and Photographic
credits
The Journal of the Morris Register, Winter 1994, Vol.14 No.8